Abstract/Summary

Lichens from the genus Umbilicaria were collected across a 5,000-km transect through Antarctica and investigated
for DNA sequence polymorphism in a region of 480–660 bp of the nuclear internal transcribed spacer region of
ribosomal DNA. Sequences from both fungal (16 ascomycetes) and photosynthetic partners (22 chlorophytes from
the genus Trebouxia) were determined and compared with homologs from lichens inhabiting more temperate,
continental climates. The phylogenetic analyses reveal that Antarctic lichens have colonized their current habitats
both through multiple independent colonization events from temperate embarkation zones and through recent longrange
dispersal in the Antarctic of successful preexisting colonizers. Furthermore, the results suggest that relichenization— de novo establishment of the fungus-photosynthesizer symbiosis from nonlichenized algal and fungal cells—has occurred during the process of Antarctic lichen dispersal. Independent dispersal of algal and fungal
cultures therefore can lead to a successful establishment of the lichen symbiosis even under harsh Antarctic conidtions.